What Causes Delay In Periods But Noticed Light Spotting?

Hello, I am 33 and my husband and I are TTC our 3rd child. I usually have brown spotting a few days before my period actually starts. This month I started to have the brown spotting 2 days before my period was to start but had 2 clots pass that day. I've never had that happen before. My period has yet to start and now I'm a day late. I only have the brown spotting mixed in with light red/pink blood.